[llvm-objdump] Default to --mcpu=future for PPC32

[MaskRay]

Summary

Extend D127824 to the 32-bit Power architecture.
AFAICT GNU objdump -d dumps all instructions for 32-bit as well.

[nemanjai]

Thanks for adding this. Nice to common-up the behaviour. LGTM.

llvm/docs/CommandGuide/llvm-objdump.rst

31

Maybe PowerPC instead of Power.

[MaskRay]

llvm/docs/CommandGuide/llvm-objdump.rst

31

Thanks for the super quick review. I was thinking of https://en.wikipedia.org/wiki/Power_ISA Power is canonical while PowerPC is the old name.
In software projects, it's true that "PowerPC" and "powerpc" are still much more common ...

[MaskRay]

change "Power" to "PowerPC". PowerPC occurs in another place in the doc.

llvm/docs/CommandGuide/llvm-objdump.rst

 
 .. option:: -a, --archive-headers
 
   Display the information contained within an archive's headers.
 
 .. option:: -d, --disassemble
 
   Disassemble all executable sections found in the input files. On some
-  architectures (AArch64, PPC64, x86), all known instructions are disassembled by
+  architectures (AArch64, PowerPC, x86), all known instructions are disassembled by
   default. On the others, :option:`--mcpu` or :option:`--mattr` is needed to
   enable some instruction sets. Disabled instructions are displayed as
   ``<unknown>``.
 
 .. option:: -D, --disassemble-all
 
   Disassemble all sections found in the input files.
 

llvm/lib/Object/ELFObjectFile.cpp

default:
     return SubtargetFeatures();
   }
 }
 
 std::optional<StringRef> ELFObjectFileBase::tryGetCPUName() const {
   switch (getEMachine()) {
   case ELF::EM_AMDGPU:
     return getAMDGPUCPUName();
+  case ELF::EM_PPC:
   case ELF::EM_PPC64:
     return StringRef("future");
   default:
     return std::nullopt;
   }
 }
 
 StringRef ELFObjectFileBase::getAMDGPUCPUName() const {

llvm/test/tools/llvm-objdump/ELF/PowerPC/mcpu.s

 ## Test that we default to --mcpu=future and disassemble all known instructions.
 ## The default is different from producers (e.g. Clang).
 # RUN: llvm-mc -triple=powerpc64le -filetype=obj %s -o %t
 # RUN: llvm-objdump -d --no-show-raw-insn %t | FileCheck %s --check-prefixes=CHECK,FUTURE
 # RUN: llvm-objdump -d --no-show-raw-insn --mcpu=future %t | FileCheck %s --check-prefixes=CHECK,FUTURE
 # RUN: llvm-objdump -d --no-show-raw-insn --mcpu=pwr9 %t | FileCheck %s --check-prefixes=CHECK,UNKNOWN
 
+# RUN: llvm-mc -triple=powerpc -filetype=obj %s -o %t
+# RUN: llvm-objdump -d --no-show-raw-insn %t | FileCheck %s --check-prefixes=CHECK,FUTURE
+
 # CHECK-LABEL: <_start>:
 # FUTURE-NEXT:   pld 3, 0(0), 1
 # UNKNOWN-COUNT-2: <unknown>
 # CHECK-EMPTY:
 
 .globl _start
 _start:
   pld 3, 0(0), 1